Deodorization of paper



Patented Apr. 25, 1933 UNITED STATES PATENT OFFICE MILTON o. SCHUR, orBERLIN, New HAMPSHIRE, ASSIGNOR rro BnowN'coMPANY, or BERLIN, NEWHAMPSHIRE, A oonronnrron or MAINE 'nEononrzArIoN on runs,

No Drawing.

The subject of the present invention is the deodorization of paperscontainingmalodorous substances as a result of the addition to thepapers of certain desirable papermaking ingredients.

I have found that papers containing malodorous substances can bedeodorized with suitable oxidizing agents so quickly that the paper maybe processed as a continuously and rapidly moving sheet, for instance,even while it is still undergoing fabrication at high speed on a papermachine, or as it comes off the paper machine. When the papercontainsmalodorous substances which react with volatile oxidizing agentssuch as the halogens or ozone, the continuous web of-paper, preferablywhile moist, can'be passed through an atmosphere of the oxidizing agent.In fact, if the paper contains the malodorous substances whileundergoing fabrication on the paper machine, the nascent Web may be onlypartial: 1y driedand then passed through the oxidizing atmosphere,whereupon the drying op- 'eration.can be completed. The presence ofwater in the web promotes the deodorizing reaction whelran atmosphere ofoxidizing agent of the 'type of chlorine or other halogens,

which are water-soluble, is relied upon for de-' 'is added to papertoweling which is otherwise ,free fromsizing or filling ingredients, the

g-toweling undergoes a multifold increase in Wet strength (as much asfive to seven times, or. more) wlthout los ng its orlgmal capacityabsorbing water.f.- When paper toweling reated' with viscose," however,1t 'assumes fan-offensiveo dbr, because of the impurities result either;from the regeneration of Application filed May 5, 1931. Serial No.535,293.

the cellulose in the viscose, or which are originally present in theviscose. Ihese impurities are largely, if not entirely, sulphurcompounds, which may impart a veryobjectionable odor to the toweling,even when present 65 in the merest traces. In working with viscose as aningredient for paper toweling, I was bothered greatly by the fact thatin some cases the offensive odors were seemingly removed when theviscose solution underwent suitable treatment, for instance, aerationand/or the action of ammonium salts, such as ammonium carbonate, addedto the viscose. Although the odoriferous impurities were indeed largelyremoved from viscose so treated, there were left in these cases traces,which, although overlooked by men who were working with the viscose andat the time the toweling was made, nevertheless were potentially ob.-noxious, especially when the toweling' was packaged, as in the usualroll form, or as interleaved sheets, in'a closed container or carton,wherethrough there was little, if any, circulationof air to carry awaythe obnoxious odors. In other words, the atmosphere of the closedcontainer or carton for the towel package-became heavily laden withtheodors progressively emitted from the traces of impurities present inthe towel package. As is well known, people working in a slightly 8odoriferous atmosphere may become oblivious to the existence of the odorbecause of adjustment of the sense of smell thereto. Yet a newcomer mayfind the atmosphere not only objectionable, but actually sickening. Forinstance, a dealer who receives a container packed with paper towelingfrom which an evil odor emanates, at once detects the odor and condemnsthe toweling. So, too, a fastidious person using the toweling, who is.working in a clean atmosphere and is hence sensitive to even slightlybad odor, is also repelled from using the paper toweling, unless it issubstantially odorless or free from objection able odor. While .aerationand/or the addition of ammonium salts to viscose before the viscose isincorporated into the paper web and then dried out at elevatedtemperature removes very nearly all of the odoriferous materialstherefrom, there may be, as already in- 1 dica-ted, sufficientodoriferous impurities left in the toweling to give rise to complaintsby the dealers and users, on account of bad odor. The process of thepresent invention not 5 only is simple, inexpensive, and eminentlypracticable, but can be applied to efl'ect the removal of all vestigesof offensive odor from paper towelin containing viscose, wherefore 'themost fastidious person can detect no evil odor in the toweling whenopening a carton containing one or more towel packages, or when using asingle towel. Very important, too, my process accomplishes the desiredend without materially detracting from the enhanced wet strength of thetoweling or seriously reducing its water absorptivity. In accordancewith my process, the web of toweling may be passed through a viscosesolution of the desired strength, squeezed free of exlustration, theviscose solution may be one of about strength in terms,of solublecellulose. The -squeezing operation may. be controlled to reduce theviscose solution content of the web to a point where the web holds itsown weight of solution, and thus has a viscose content in terms .ofsoluble cellulose, based on fiber, similar to that of the impregnatingsolution, viz., 4%. The dried viscose-containing web may then be passedthrough a dilute chlorine solution, say, one

containing up to about 0.5% chlorine, then squeezed free of excesssolution, and finally dried. The odoriferous or odor-generatingsubstances introduced into the toweling along with the viscose isthereby entirely eliminated.

Solutions of other oxidizing agents, such as hypochlorite and sodium orhydrogen peroxide, may be used instead of chlorine water. When ahypochlorite is used, it is preferably the hypochlorite of a highlysoluble base, such as sodium, which class o'fhypochlorite does notdeposit difiicultly soluble residues in the toweling. An advantage ofthe deodorizneed not be washed after treatment with the oxidizing agent,but may be at once redried without noticeable efi'ect upon either itsdry or wet strength, or uponits capacity for abtilization of the morevolatile sulphur-cont.

cess solution, and then dried. By way of il-v ing treatment described isthat the toweling sorbing water. One may, however, subject pounds by theheat applied during an intermediate drying operation. -In other words,

sufiicient additional oxidant is used. to react with the volatilesulphur compounds, which would otherwise be expelled from the towelingby heat. It is my theory that by my process, not only are the sulphurimpurities oxidized in situ in the toweling into colloidal sulphur,which does not interfere materially with water absorption by thetoweling, but further, that regeneration of cellulose from the viscoseis hastened and made substantially complete on the drier, so that thereis very little chance for after-regenerating efi'ects, ac-

companied by the formation of evil odors in the dried toweling.

When the toweling is passed through .vis- I:

'cose solution and then squeezed there is retained in the toweling, ashereinbefore described, about an equal weight of solution containingviscose based on dissolved cellulose. When the impregnated towelisintroduced directly into the oxidizing solu-' tion, it immediatelyabsorbs the solution to an extent which depends upon the time of contactand upon the characteristics of 'the solution, and the characteristicsof the fiber comprising the toweling. The maximum amount of oxidizingsolution taken up by a kraft towel, for example, may be about to 150%the weight of the fiber. The oxidizing solution mingles in the pores ofthe sheet with the viscose solution and when a moment later the towel:is again passed through squeeze rolls to facilitate drying, the mixedsolutions are squeezed out of the pores. Now v1t is an important andinteresting discovery that substantially no appreciable quantities ofsoluble cellulose or regenerated cellulose a-re squeezed outof thepores. That is to say, the oxidizing solution precipitatesthe solublecellulose within the pores. This 'precipitation may be due partly to asalting-out effect, partly to a breaking up of the xanthate by oxidationof the sulphur contained in it,

or by precipitation of the xanthate, depending upon the type ofoxidizing solution used. If it were not for this precipitation withinthe pores of the towel it wouldobviously be very wasteful of bothviscose and oxident, for more viscose would have to be added, thancorresponded to the amount of regenerated cellulose needed in the finaltowel,'the'ex'cess being equal to that quantity which would be squeezedout during the second pressing. That the very small quantities ofoxidizing agents needed will fix the soluble cellulose within the poresof the fibre, consequently represents an important phase of myinvention.

. A third mode of procedure, in accordance with'mv invention depends onthe use of an oxidizing atmosphere, rather than anoxidlZlIlgflSOlllt-IOII. In such case, the toweling 1s impregnated withthe vlscose solution 1n the usual way, is then passed over a bankofdrier rolls, and while still moist is assed through an oxidizingatmosphere a ordedas by chlorine or other halogen. The toweling thusdeodorized is then passed over another bank of drier rolls, by which itis substantially completely'dried. The concentra tion of the halogen inthe oxidizing atmosphere, and the time of exposure of the toweling tothe oxidizing atmosphere, are regulated so that the toweling issuescompletely deodorized from the oxidizing atmosphere, readyforfinal-stage drying. It is easy to regulate the conditions oftreatment in the oxidizing atmosphere to efl'ectdeodorization of thetoweling without injuring the fiber, as aresult of oxidation and/orhydrolysis of the cellulose into oxycelluloses, as thedeodorizing'reaction is evidently quite selective and, 'as alreadyindicated, proceeds to completion in an exceedingly short period oftime. In lieu of an oxidizing atmosphere furnished by chlorine or otherhalogen, other oxidizing atmospheres, e. g., an ozone-containingatmosphere, may be used. 7

It is a surprising phenomenon that viscosecontainiug toweling can becompletely and permanently deodorized without being chemically orphysically injured, and further, that such deodorization is accomplishedeven when oxidized impurities are permitted to remain in the toweling.In this connection, it is to be observed that in the manufacture ofpaper toweling, the manufacturer often employs the strongest availablewood pulp, soas to realize the strongest toweling attainable from thewood fiber alone. .To this end, kraft pulp, which is the strongestchemical wood pulp, is chosen as the cellulose base. Kraft pulp,however, contains a notable residue of ligneous material, since thekraft process of fiber liberation is less selective on hgnocellulosesthan are other chemical pulping processes, such as the sulphite process.The tancolored, raw kraft pulp is customarily used as such, on accountof the high bleach usage necessary to whiten such pulp, and theinjurious effect of such bleach usage on fiber strength. It isremarkable that, despite the fact that lignin reacts almostinstantaneously with an oxidizing solution, especially chlorine waterand hypochlorite liquor,nevertheless the desired elimination ofodoriferous sulphur residues from kraft toweling'can be accomplishedthrough the use of only small quantities of oxidants. In other words,al-

. though ligneous matter can be removed selectively from kraft pulpalone with small amounts of chlorine water or equivalent oxidant, yetthe reaction of such oxidants upon thesulphur impurities introduced intothe pulp by viscose is'eyidently even more selective and can proceedselectively to completion in the presence of a large excess of ligneousmatter. My process, while applicable to paper toweling made from pulpfurnishes of a wide variety, is specifically adapted to theintrinsically strong paper toweling fabricated from kraft pulps.

One phase of my inventlon involves the introduction of the viscose intothe paper- -making stock in the beater engine, into the stock while itis on its way to the paper machine, or, into the stock after it has been7, formed as a nascent web on the paper ma chine. -In suchcase, theviscose-containing web, after only partial drying on the paper Imachine, can be passed through an atmosphere of oxidizing agent whichdeodorlzes the web completely and permanently as hereinbefore described.The deodorized and partially dried web may then be dried to completion.Such a process avoids the necessity for redrying the paper and thusmeans that my invention can be practised inexpensively and with thesimplest kind of apparatus. Thus, the viscose-containing web may bedried on the paper machine to a fiber content of, say, about 65% towhereupon the partially dried web may be passed through anoxidizingatmosphere. At this stage-pf dryness, the volatilizable sulphur impurites have been largely expelled by heat and the web may be festooned orotherwise supported without breakage in the oxidizing chamber to permitsufiicient time of exposure to the 0x1- dizing atmosphere. At this stageof drynes s, however, there is still sufiicient moisture in the web topromote a smooth and rapid reaction between a gaseous oxidizing agent,

such as chlorine, and the oxidizable, odoriferous impurities present inthe web.

When theoxidant is used in solution, I have found that it is best tosegregate the ox1d1z ing solution squeezed from the web, immedlatelyafter impregnation, from the main bath of oxidizing solution. When thedry web of toweling is dipped in the oxidizing solution, say, in watercontaining say, .05%

chlorine, it may absorb about 2 to 3 times its weight of solution,whereuppn it 15 run through a pair of press rolls ad]usted.to re- -moveall but, say, its own weight-of solution.

The solution squeezed from the toweling is substantially devoid ofoxidizing agent, having been completgly' exhausted in the short intervalof time between its introduction into the toweling and expulsion of theexcess by the press-rolls. The spent oxidizing solution should hence notbe directed to. the main bath of oxidizing solution, as it would simplycontaminate the bath and render the control of the composition of thebathadifficult matter.

As already indicated, the viscose-treated such washing is necessary.When wash. water is used after the oxidant treatment, no

difiiculty is encountered, since not only has the toweling been enhancedin wet strength by the viscose treatment so as to withstand ruptureunder stress in a bath of wash water,

but the viscose has been rendered water-insoluble by the oxidizingtreatment, and hence is not leached out by the wash water.

I claim:

1.- As an article of manufacture, dried, viscose-treated paper entirelyand permanently free from malodors. -2. .As an article of manufacture,dried, vis cose-treated paper toweling entirely free from evil odors andfromsubstances which generate evil odors.

3. As an article-of manufacture, paper toweling treated with about 1%viscose, calculated as soluble cellulose,'based on the' stroy fou odorsand odor-generating subsubstances in such stances in such paper.

7. A process which comprises treating viscose-containing paper with anoxidizing agent to destroy foul odors and odor-generating substances insuch paper, and washing; the paper with water to remove water-solubleproducts.

8. A process which comprises treating viscose-containing paper with -asolution of an oxidizing agent to destroy foul odors and odor-generatingsubstances in such paper, and drying. the deodorized paper.

9. A step which comprises treating viscosecontaining paper with agaseous oxidizing agent to destroy foul ,odors and odor-generatingsubstances in such-paper. 1

10. A process whichcomprises treating wet, viscose-containing paper witha gaseous oxidizing agent to destroy foul. odor and odor-generatingsubstances in such paper, and drying the deodorized paper.

11. A process which comprises treating the wet viscose-containing paperwith [chlorine gas to destroy foul odor and odor-generating odorizedpaper. I

12. In the manufacture of viscose-treated papers permanently free fromevil odors,

those steps which comprise running paperinaking pulp off on apapermakingmachine as a continuous web of paper, progressively treatingthe web as-itcomes from the machine with a viscose solution,progressively treating the viscose-containing web with an oxipaper, anddrying the dedizing solution to destroy foul odor and odorgeneratingsubstances in the web, and pro gressively drying the deodorized web.

13. A processwhich comprises only partially drying a nascent wet web ofpaper associated with viscose, passing the partially dried web throughan atmosphere of oxidizing gas to destroy foul odor and odor-genergas todestroy foul odor and odor-generating substances in the web,andcompletely drying the web.

16. A process which comprises treating a web of wateirleaf paper with aviscose solution, drying, treating the dried, viscose-containing paperwith a solution of an oxidizing agent to destroy foul odor andodor-generating substances in the web, and redrying.

17. A process which comprises treating a web of Waterleaf paper with aviscose solution, partially drying, treating the partially dried,viscose-containing paper with a watersoluble, gaseous oxidizing agentvto destroy foulodor and odor-generating substances in the paper, anddrying to completion.

18. A process which comprises treating a web of cellulose with a viscosesolution, treating the viscose-containing paper with a solution ofoxidizing agent to destroy foul odor and odor-generating substances inthe web, squeezing the web to remove excess solution, and drying.

19. A process which comprises progressive 1y treating acontinuous web ofcellulose with a a. viscose solution, progressively passing theviscose-containing web through a bath of oxidant solution to destroyfoul odor and odor-generating substances in the .web, squeezing the webto removeexcess solution, segregating the removed solution from the bathof. oxidant,- and progressively drying the web.

20. A process which comprises progressignature.

. MILTON O. SCHUR.

